This application relates to a mold gate which works effectively for all molding compounds, but exhibits the added advantage of working effectively with ultra-stiff molding compounds, for example, glass-filled materials and the like, as may be used for molding high-strength buckets or any other desired item.
Conventionally, it has been proven to be difficult to inject very stiff molding compounds into an injection molding system through a mold gate. Even if ultra-high pressure injection is used, stagnant areas can develop in the mold gate, where degradation of the molding compound can take place.
Particularly in the case of thin-walled plastic molded members such as the bottom of a bucket, the stiff molding compound typically in the prior art enters in perpendicular relationship to the narrow channel of the mold which defines the bucket bottom. The turning of the stiff molding compound and its spreading through the narrow channel serves as a major source of flow resistance, so that even large capacity injection mold systems pass such compound only with difficulty through the orifice of the mold gate when a small, centrally-located orifice in the mold gate is used.
By another technique, a mold gate with a larger orifice may be used to reduce flow resistance, but this leaves a large, projecting sprue from the bottom of the bucket which then must be cut away.
In accordance with this invention, a mold gate is provided, causing easier injection of stiff molding compound into the mold cavity, especially when the cavity is of very narrow dimensions such as the bottom of a bucket, while avoiding stagnant areas in the mold gate and consequent scorching or burning of the molding compound. Furthermore, in this invention, a shortened sprue may be obtained, being provided by the reinforced, thin-walled characteristic of the mold gate.
Accordingly, it becomes possible by the use of the mold gate of this invention to injection mold ultra-stiff materials, which had previously been impractical for use in injection molding machinery of similar capacity while using a conventional mold gate.